In a traditional mobile network, all communication between user equipment (UE) devices goes through a base station, even if two UE devices communicating with each other are in close physical proximity.
Device-to-device (D2D) communication has more recently been introduced to allow for UE devices in close physical proximity to directly communicate with each other without using the base station.
As the number of UE devices in a mobile network increases, there may be more potential opportunities for D2D communication.